This application claims priority under 35 U.S.C. xc2xa7xc2xa7119 and/or 365 to GB 0019059.5 filed in United Kingdom on Aug. 4, 2000; the entire content of which is hereby incorporated by reference.
This invention relates to a catheter adapter. The inventive adapter can assist in preventing bacteriological material passing into the sterile fluid pathway.
Many medical procedures require the use of tubes or catheters to transmit fluids to or from the patient. Some catheters can be inserted through natural orifices, but others are inserted through needles or other surgical procedures, where the catheter tip can be sited in sensitive and critical organs.
The external ends of these catheters usually require adapters to be fitted so that medical equipment can be attached either for the collection or distribution of fluids. The adapter is required to have means for securely connecting to the catheter and to the medical device with joints that seal against leakage.
Epidural catheters, for example, operate in this manner, whereby a flexible plastics catheter is introduced through a needle into the patients epidural space. After insertion an adapter is fitted to the external end of the catheter which grips and seals against the catheter, the other end of the adapter having a luer lock connector for attachment to a drug delivery system.
Drug bearing fluids can then be administered through the adapter and catheter into the patients epidural space. The security of grip, efficiency of use and the integrity of the sealing arrangements provided by the adapter are important for ensuring that bacteriological matter is not transferred through the adapter connection points into the catheter and epidural space, with serious implications for patient safety.
Prior art epidural adapters generally employ a cylindrical soft resilient element, typically 5 mm outside diameter by 12 mm long, which is captive within the adapter, to seal and grip against the catheter. The catheter is located through the centre of the flexible element and most commonly a screw cap is provided to axially compress the element. Because the element is externally constricted by the connector body, when the element is compressed by the screw cap, the internal pathway of the element is contracted, gripping and sealing against the catheter. Because the axial force applied to the element is perpendicular in direction to the radial gripping force applied by the element to the catheter the mechanism is mechanically inefficient. As catheters are also of resilient material the element is required to radially compress the catheter by a significant amount to achieve an effective grip on the catheter. Consequently the element requires a relatively large axial force and displacement to sufficiently deform the element to grip the catheter.
Because of the dual function to seal and grip the catheter the size and material characteristics of the resilient element have to be selected to fulfill both requirements.
The integrity of the catheter connection is dependent in part on how hard the screw nut is tightened, resulting in variable rates of sealing and grip, with the clinician not necessarily knowing the correct level of tightness required to achieve an adequate connection. Furthermore this type of connection gives no visible indication as to how tight or secure the connection is, and in circumstances where the connection had not been tightened enough, or had been accidentally released no warning of the condition is indicated by the adapter.
As the luer lock connection to the medical device is also a screw type locking action, when attempting to release the medical device the clinician may release the catheter connection by mistake. Under these circumstances reconnection of the catheter would not be safe, and the catheter would have to be withdrawn from the patient, and a new sterile catheter inserted with the attendant cost of the procedure and the risk and distress to the patient.
Furthermore the luer lock connector is such that external parts of the connector immediately adjacent to the sealing faces are exposed to touch, and bacterial contamination can easily build up around the connector hub. When breaking this seal to disconnect a medical device such as a biological filter the bacteriological material can be very close to the sterile fluid pathway, with the potential for infectious material being introduced into the sterile fluid pathway, especially during the reconnection of the medical device.
We are aware of patent specification GL 1505349. This discloses an adapter in which a length of flexible resilient tubing through which the catheter extends is gripped between two hinged members that can be clipped together in an operative position in which a semi-circular retaining member is held against a localized portion of the resilient tubing. Again, the resilient tubing is relied upon both to grip the catheter and to effect a seal therewith.
According to one aspect of the present invention there is provided a catheter adapter comprising an adapter body, a medical device securing means for releasably securing and hermetically sealing the adapter body to a medical device, and catheter securing means for releasably securing and hermetically sealing the adapter body to a catheter of predetermined external diameter, the catheter securing means comprising first and second rigid elements provided with confronting surfaces, and an operating device adapted to urge the rigid elements towards one another, at least one of said confronting surfaces comprising longitudinal channel walls defining a channel, whereby the confronting surfaces combine together to define a close tolerance pathway when the elements are urged towards one another by the operating device, and an operating device retaining means for retaining the operating device in an operative position, the catheter adapter being such that, in use, each rigid element is moved as a whole towards the other rigid element, the size of the said pathway being such that in use a length of a catheter enclosed within the pathway is compressed and held by engagement of said rigid elements with the catheter, the operating device comprising seal biassing means by which a resilient sealing element is also compressed against the catheter and urged against the adapter body to form a fluid seal therebetween whilst the operating device is in the operative position.
Although it would be possible for only one of the rigid elements to be formed with a channel, preferably both elements are provided with respective longitudinal channels that combine together, in the operative condition, to define the close tolerance pathway.
The elements desirably abut one another in the operative condition, but it would be possible for the elements to be spaced apart by a small amount.
In one embodiment of the invention the means for releasably securing and hermetically sealing the adapter to a medical device is a standard luer lock connection.
The rigid elements are preferably provided with a plurality of transverse ridges protruding into and extending around, or partially around, the longitudinal channels such that when the elements are pressed together the catheter enclosed within the pathway formed by the channels is locally deformed and gripped by the series of ridges.
In one embodiment of the invention the operating means comprises a screw type nut.
In another embodiment of the invention the operating means comprises a lever so arranged that when the connector mechanism is in the open position the lever arm is at an angle to the adapter body, and when the lever arm is rotated fully to secure the catheter it lies substantially parallel to the adapter body, the position of the lever arm providing indication that the catheter is connected.
The releasable securing means is preferably a sleeve located around the adapter body and having means to slide axially within limits with respect to the adapter body, the sliding sleeve also having means to rotate the adapter body, the adapter configuration being such that when the lever arm is fully rotated to secure the catheter a spring acting against the sleeve slides the sleeve over the end of the lever arm releasably securing the lever arm against the adapter body.
The sleeve may engage with the medical device to which the adapter is connected to form a shield around the luer lock connector.
The sleeve around the adapter may be adapted to engage with the medical device to which the adapter is connected to restrict movement of the sleeve thus forming an interlock stopping the release of the catheter connector.
Two adapters in accordance with the invention will now be described by way of example only, with reference to the accompanying drawings.
Rigid elements can each be provided with an element camming formation, with the operating device arranged to urge the rigid elements axially against a body camming formation provided on said body, the co-operation of the camming formations causing the rigid elements to be pressed together as the operating device is moved towards the operative position.
An adapter body can be provided with a stepped bore, and with the element camming formation having a rounded corner on each of the elements, and the body camming formation comprising a pair of shoulders defined by the outer ends of a pair of flats in the larger diameter portion of the body bore.